During the production of a structure, for example a surface ship or a submersible, after making or laying the main elements of the structure, such as the hull or the main subdivisions of the latter, a phase occurs for implanting various secondary pieces on the elements of the structure. The secondary pieces are for example ties, beds, structural parts or further pieces awaiting to be equipped, such as electrical pieces of equipment or equivalent. For a medium tonnage ship, such as a frigate, the matter is thus to position and attach about 50,000 pieces.
Presently, on the building site, an operator positions a piece on a structural element by means of a paper blueprint made in a design department, and then printed out. The dimensions indicated on this blueprint should be taken relatively to a local reference system of the structure also indicated on the blueprint. For each piece to be positioned, the operator should then identify, in position and in orientation, the local reference system. The operator then has to copy out, on the wall of the structural element, the dimensions indicating the suitable position and orientation with respect to the local reference system, of the surface of the piece, or base, bearing upon the structural element.
This conventional positioning method requires a substantial amount of time, not only for preparing the blueprints, but especially for using them on the site. Further, this method has the drawback of resorting to a local reference system. Further, under the particularly difficult conditions of a building site (congestion, shadowy light, etc.), the reading of the blueprints and the taking of measurements often carried out by hand are sources of errors on the exact positioning of the piece.
In order to optimize the positioning of the piece on the structural element prior to its attachment, the use of positioning aid systems was proposed, allowing the outline of the base imprint of the piece to be projected on the wall of the structural element used as a screen. The projection is made so that it accurately plots, in position and in orientation, the area for implanting the piece. Such a system, used in the building of aircraft, is disclosed by document WO2005/025199 A2.
The secondary pieces to be attached on the wall of a structural element of a ship are often ties for supporting a piece of equipment, the latter not being directly attached against the wall of the structural element. The tie is thus provided with connecting means intended to cooperate with conjugate connecting means provided on the piece of equipment to be supported.
A tie is generally a profile, the base of which substantially corresponds to a cross-section. That is to say that the tie is intended to be attached on the wall so that its longitudinal axis extends substantially parallel to the direction normal to the wall, at the implantation area. The means for connecting such a profiled tie are often located in the vicinity of the end of the tie, opposite to the base.
Now, as the tolerance margins on such secondary pieces are wide, it is possible that, although the base is properly positioned inside the outline projected on the wall of the structural element, the longitudinal axis of the tie is not properly oriented relatively to the direction normal to the wall. Accordingly, once the tie is attached, its connecting means do not have the required position and orientation, which may be a problem for cooperating with the conjugate connecting means of the piece of equipment to be supported.
The particular case of the positioning of a profiled tie, oriented substantially perpendicularly to the wall of the structural element, is illustrative and exacerbates the general problem of accurately spatially positioning a piece to be implanted on the wall of an element of a structure.